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Query: UMLS:C0851184 (thinning)
 11,252 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Superpacking of chromatin and the surface features of metaphase chromosomes have been studied by SiO replication of wet, unstained, and unfixed specimens in an exceedingly thin (less than or equal to nm) aqueous layer, keeping them wet. Hydrophilic Formvar substrates allow controlled thinning of the aqueous layer covering the wet specimens. Whole mounts of chromatin and chromosomes were prepared by applying a microsurface spreading method to swollen nuclei and mitotic cells at metaphase. The highest level of nucleosome folding of the inactive chromatin in chicken erythrocytes and rat liver nuclei is basically a second-order superhelical organization (width 150--200 nm, pitch distance 50--150 nm) of the elementary nucleosome filament. In unfavorable environments (as determined by ionic agents, fixative, and dehydrating agetns) this superstructure collapses into chains of superbeads and beads. Formalin (10%) apparently attacks at discrete sites of chromatin, which are then separated into superbeads. The latter consist of 4--6 nucleosomes and seemingly correspond to successive turns of an original solenoidal coil (width 30--35 nm), which forms the superhilical organization. When this organization is unfolded, eg, in 1--2 mM EDTA, DNAse-sensitive filaments (diameter 1.7 nm) are seen to be wrapped around the nucleosomes. The wet chromosomes in each metaphase spread are held to each other by smooth microtubular fibers, 20--20 nm in diameter. Before they enter into a chromsome, these fibers branch into 9--13 protofilaments, each 5 nm wide. The chromosome surface contains a dense distribution of subunits about 10--25 nm in diameter. This size distribution corresponds to that of nucleosomes and their superbeads. Distinct from this beaded chromosome surface are several smooth, 23--30-nm-diameter fibers, which are longitudinal at the centromere and seem to continue into the chromatid structure. The surface replicas of dried chromosomes do not show these features, which are revealed only in wet chromosomes.
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PMID:Superstructures of wet inactive chromatin and the chromosome surface. 11 65

Human adult keratinocytes migrating on a nonviable dermal substrate in cultures without fibroblasts induce thinning and degradation of the collagen substrate beneath the migrating epithelium. Further, unconcentrated conditioned medium from the cultures exhibit collagenolytic activity against both type I and type IV collagen which is inhibited by EDTA but not by phenylmethylsulfonyl fluoride or N-ethylmaleimide. Since the migrating epithelium and dermal substrate do not contain fibroblasts, this study shows that migratory keratinocytes in contact with interstitial collagen are capable of producing collagenases against type I and type IV collagen. Moreover, migratory keratinocytes appear to be similar to highly metastatic cells in their ability to degrade basement membrane collagen.
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PMID:Adult human keratinocytes migrating over nonviable dermal collagen produce collagenolytic enzymes that degrade type I and type IV collagen. 242 16

Some patients who undergo aortocoronary bypass develop lesions in the graft and recurrence of symptoms. Hydraulic distension is used for preparation of veins. We have studied properties of vein interstitium, before and after peroperative distension, in 30 consecutive unselected patients. Segments of vein were studied for water content, swelling behaviour, tracer distribution, and uronic acid content. Initial water content was the same in distended and undistended vein; initial uronic acid content was slightly lower in distended veins, 8.7 (SD = 2.3) micrograms/m, n = 4 vs 10.5 (SD = 5.1) micrograms/mg dry weight, n = 6, not significant. The initial ratio, uronate/hydroxyproline was less in distended veins, 0.14 (SD = 0.05) n = 4 vs 0.19 (SD = 0.07), n = 6 in controls, not significant. Distended veins swelled less during incubation in saline. Average weight gain/initial weight was 0.65 (SD = 0.45), n = 27, and 1.1 (SD = 0.66), n = 25 in controls (p less than 0.01); change in water content/dry weight was 1.2 (SD = 1.1), n = 22, and 1.7 (SD = 1), n = 23 (p less than 0.02), in controls. Distended veins desorbed less uronic acid into the bath; 0.40 (SD = 0.2) microgram/mg wet tissue, n = 26 and 0.59 (SD = 0.3), n = 25 in controls (p less than 0.01). The pattern of uptake of two tracers 125I Serum albumin and 51Cr EDTA, was similar in both groups. These findings suggest alteration of the interstitial matrix of veins during distension. Histologic examination of glutaraldehyde-fixed tissue by light and electron microscopy revealed mural thinning and endothelial cell damage in distended veins.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Changes in vein interstitium following distension for aortocoronary bypass. 260 Jan 35

The fusion of large unilamellar phosphatidylserine liposomes (PS LUV) induced by La3+ has been monitored using the 1-aminoapthalene-3,6,8-trisulfonic acid/p-xylenebis(pyridinium bromide) (ANTS/DPX) fluorescence assay for the mixing of aqueous contents. The fusion event is extensive and nonleaky, with up to 95% mixing of contents in the fused liposomes. However, addition of excess EDTA leads to disruption of the fusion products in a way that implies the existence of metastable intermembrane contact sites. The maximal fusion activity occurs between 10 and 100 microM La3+ and fusion can be terminated rapidly, without loss of contents, by the addition of excess La3+, e.g., 1 mM La3+ at pH 7.4. This observation is explained by the very large intrinsic binding constant (approximately 10(5) M-1) of La3+ to the PS headgroup, as measured by microelectrophoresis. Addition of 1 mM La3+ causes charge reversal of the membrane and a large positive surface potential. La3+ binding to PS causes the release of a proton. These data can be explained if La3+ can chelate to PS at two sites, with one of the sites being the primary amino group. This binding model successfully predicts that at pH 4.5 fusion occurs up to 2 mM La3+, due to reduced La3+ binding at low pH. We conclude that the general mechanism of membrane fusion includes three kinetic steps. In addition to (a) aggregation, there is (b) the close approach of the surfaces, or thinning of the hydration layer, and (c) the formation of intermembrane intermediates which determine the extent to which membrane destabilization leads to fusion (mixing of aqueous contents), as opposed to lysis. The lifetime of these intermembrane intermediates appears to depend upon La3+ binding to both PS sites.
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PMID:La3+-induced fusion of phosphatidylserine liposomes. Close approach, intermembrane intermediates, and the electrostatic surface potential. 338 13

The kinetics of peptidoglycan degradation were examined under different conditions of autolysis of Escherichia coli. With cephaloridine- or moenomycin-induced autolysis, degradation did not exceed 25 to 35%, whereas in EDTA-induced autolysis it rapidly reached 65 to 70%. When nonautolyzing cells were fixed overnight with glutaraldehyde, followed by an osmium fixation, and thin sections were stained by the phosphotungstic acid method, a dark, 15-nm-thick layer of uniform appearance and constant width occupied the whole area between the inner and outer membranes of the envelope. The stained material was tentatively identified with peptidoglycan. Ultrastructural changes in this phosphotungstic acid-stained periplasmic space were investigated at different time intervals after induction of autolysis. In all cases, breakdown proceeded over the whole cell surface. During antibiotic-induced autolysis a progressive thinning down limited to the inner side of the layer was observed. During EDTA-induced autolysis, the rapid decrease in thickness correlated well with the important loss of material labeled with [3H]diaminopimelic acid. Considering these changes and the insufficient amounts of peptidoglycan (1.3 U/nm2) necessary to account for a regularly structured polymer occupying the whole 15-nm layer, it was speculated that peptidoglycan might be unevenly distributed throughout the periplasmic space.
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PMID:Correlation between degradation and ultrastructure of peptidoglycan during autolysis of Escherichia coli. 391 20

The formation of two spherical model membranes at the tips of two syringes has allowed us to study the role of gangliosides in membrane adhesion and look for changes in conductance between two such membranes during the process of adhesion. Membranes were formed in aqueous 100 mM NaCl, 10 mM KCl, 1 mM CaCl2 from 1% (w/v) egg phosphatidylcholine in n-decane, with or without mixed bovine brain gangliosides. After thinning to the 'black' bilayer state, two membranes were moved into contact. With gangliosides, the contact area and conductance increased colinearly with time over a 5 to 20 min period of adhesion. The role of electrostatic bridging by calcium was investigated. In the absence of calcium or in the presence of 2 mM EDTA, adhesion proceeded after a longer lag time at about one-half the normal rate. As the ganglioside concentration was increased from 0 to 15 mol%, the electrical conductance of individual membranes decreased 3-fold from 48 +/- 30 nS/cm2 to 17 +/- 13 nS/cm2. The conductance was pH dependent with a minimum at neutral values. At neutral pH, when two membranes containing 4.1 mol% gangliosides adhered, the region of adhesion had a specific conductance three times that of the nonadhering regions of membranes. Without gangliosides, the specific conductance of the contact region was the same as that of non-adhering regions of the membrane. These data suggest that mixed gangliosides can mediate an adhesion-dependent increase in conductance.
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PMID:Role of gangliosides in adhesion and conductance changes in large spherical model membranes. 647 10

Two experiments were conducted to produce Zn deficiency in, and to establish approximate Zn requirements of, the cat. In experiment 1, soy protein (SP)-based diets were fed for 8 months: diet 1, basal, without added Zn, 15 ppm; diet 2, basal, 15 ppm Zn plus 2% CaHPO4; and diet 3, basal with added Zn, 67 ppm. Gross Zn deficiency symptoms were not observed, although spermatogenesis in cats fed diets 1 and 2 was abnormal. There were no differences in food intake or growth rate between treatments. Mean plasma zinc levels (micrograms/100 ml) for cats fed diets 1, 2 and 3 were 55, 47 and 89, respectively. In experiment 2, the SP was washed with EDTA. Ten 8-week-old kittens were fed the following diets for 14 weeks: diet 4, SP without Zn, 0.7 ppm Zn; diet 5, containing 52 ppm Zn; or diet 6, an amino acid diet, 4.8 ppm Zn. Mean food intake (g/day) and weight gains (g/day) for cats fed diets 4, 5 and 6 were: 17.2, 0.4; 55.0, 19.5; and 31.5, 10.0, respectively. Mean plasma Zn levels (micrograms/100 ml) and liver Zn (ppm) for cats fed diet 4 had poor coats characterized by thinning and slow hair growth and scaliness of the skin and ulcerations of the buccal margins. The cat's requirement for zinc is probably between 15 ppm and 50 ppm.
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PMID:Zinc deficiency in the cat. 720 4

Glucose degradation products (GDP) are carbonyl compounds, that are formed by heat sterilization of conventional peritoneal dialysis (PD) fluids. Carbonyl compounds are known to be toxic in vitro and potentially toxic also in vivo. The aim of this study was to evaluate the effects of daily, short-term exposure of the peritoneum to very high concentrations of GDP in vivo on peritoneal transport parameters and on peritoneal morphology in a well-established rat model of PD. Rats were exposed to three daily intraperitoneal (IP) injections (10 ml) for 9 days of a largely neutral (pH 7.2) PD fluid containing 1.5% glucose and sterilized by filtration, with (n = 8) or without (n = 8) the presence of different carbonyl compounds in concentrations 100 times higher than those reported in commercial PD fluids. Seven rats, not subjected to any exposure, served as controls. After the exposure, the rats were subjected to acute PD in 4-hour dwells. Twenty milliliters of 4% glucose dialysis fluid were instilled into the rat peritoneal cavity. Blood and dialysate samples were taken during the dwell for measurements of dialysate sodium, and for assessments of the mass transfer area coefficient (PS) for glucose and 51Cr-EDTA and of transperitoneal clearance (Cl) or radiolabelled albumin (RISA). At the end of the dwell, parts of the liver, diaphragm and peritoneum were removed for measurements of tissue cell density and thickness of the submesothelial peritoneal tissue. The exposure of the peritoneum to very high doses of carbonyl compounds did not affect the peritoneal transport of fluid and small solutes significantly, but seemed to slightly reduce lymph flow and albumin clearance out of the peritoneal cavity. Assessed after a hypertonic dwell, and compared to the situation in nontreated rats after the same kind of dwell, there was a significant thinning of the submesothelial tissue, but no difference in tissue cell density. It is concluded that short-term exposure of the peritoneum in vivo to very high doses of GDP resulted in almost no signs of acute toxicity.
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PMID:Very high daily intraperitoneal doses of carbonyl compounds affect the morphology, but not the exchange characteristics, of rat peritoneum. 1124 88

Fourteen commercial LM-pectin samples were investigated in this study. The degree of esterification (DE) varied from 9.6% to 42.0% and the degree of amidation (DA) from 0% to 25%. Chemical and structural characteristics were examined using atomic absorption (AA), dilute solution capillary viscometry, GPC-MALLS and dynamic light scattering. The intrinsic calcium was in the range of 47-1388 ppm, the intrinsic viscosity varied from 2.9 to 4.9 (dL/g) and the weight average molecular weight (M(w)) from 113 to 290 (kDa). Most of the samples had Huggins constants of ~0.5. However, for samples having acidic pH, Huggins constant values greater than 1, which can be as an indication of aggregation, were obtained. The high Huggins constant value could be reduced to ~0.5 by the addition of 3M urea, indicating that the aggregation was stabilised by hydrogen bonding. Shear flow viscosity revealed three types of rheological behaviour. Type A showed pronounced shear thinning behaviour, which was reduced by the addition of hydrogen bonding breaking agent urea. Type B with intrinsic Ca of 1mM and pH ~4 showed two shear thinning regions, with significantly enhanced shear viscosity upon addition of calcium. Type C showed the least aggregation due to its pH ~4 and low intrinsic Ca, but could be converted to type B upon addition of Ca. The effect of Ca on the rheological behaviour of types B and C was further confirmed by CaCl(2) and Ca-chelating agent (EDTA). Temperature affected the molecular conformation of all types and most significantly type A by eliminating the hydrogen bonding.
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PMID:Characterisation of commercial LM-pectin in aqueous solution. 2339 38

We investigated experimentally the rheological behavior of whole human blood subjected to large amplitude oscillatory shear under strain control to assess its nonlinear viscoelastic response. In these rheological tests, the shear stress response presented higher harmonic contributions, revealing the nonlinear behavior of human blood that is associated with changes in its internal microstructure. For the rheological conditions investigated, intra-cycle strain-stiffening and intra-cycle shear-thinning behavior of the human blood samples were observed and quantified based on the Lissajous-Bowditch plots. The results demonstrated that the dissipative nature of whole blood is more intense than its elastic component. We also assessed the effect of adding EDTA anticoagulant on the shear viscosity of whole blood subjected to steady shear flow. We found that the use of anticoagulant in appropriate concentrations did not influence the shear viscosity and that blood samples without anticoagulant preserved their rheological characteristics approximately for up to 8 minutes before coagulation became significant.
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PMID:Shear viscosity and nonlinear behavior of whole blood under large amplitude oscillatory shear. 2439 9


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